Friday, September 25, 2009

Climate Change Speeding Toward Irreversible Tipping Points

Environment News Service, 25 September 2009

WASHINGTON, DC, September 25, 2009 (ENS) - The speed and scope of global warming is now overtaking even the most sobering predictions of the last report of the Intergovernmental Panel of Climate Change, finds a new report issued by the United Nations Environment Programme, entitled "Climate Change Science Compendium 2009."

A set of facts compiled in association with scientists around the world, the report comes less than 75 days before the crucial UN climate convention meeting in Copenhagen. There world leaders are expected to agree on a new treaty limiting greenhouse gas emissions to replace the Kyoto Protocol, which expires at the end of 2012.

This new analysis of the latest, peer-reviewed science indicates that many predictions at the upper end of the Intergovernmental Panel of Climate Change's forecasts are becoming more likely. Some events thought likely to occur in the long-term are already happening or will happen far sooner than had previously thought, the report shows.

The report underlines concern by scientists that the planet is now committed to damaging and irreversible impacts as a result of the greenhouse gases already in the atmosphere.

The growth in carbon dioxide emissions from energy and industry has exceeded even the most fossil-fuel intensive scenario developed by the IPCC at the end of the 1990s. Global emissions were growing by 1.1 percent each year from 1990-1999 and this accelerated to 3.5 percent per year from 2000-2007.

Yet the scientists documented in the Compendium suggest that it may still be possible to avoid the most catastrophic impacts of climate change, but only if there is immediate, cohesive and decisive action to both cut emissions and assist vulnerable countries to adapt.

In his foreword to the Compendium, UN Secretary-General Ban Ki-moon writes, "The science has become more irrevocable than ever: Climate change is happening. The evidence is all around us. And unless we act, we will see catastrophic consequences including rising sea-levels, droughts and famine, and the loss of up to a third of the world's plant and animal species."

"We need a new global agreement to tackle climate change, and this must be based on the soundest, most robust and up-to-date science available," writes the secretary-general. "We need the world to realize, once and for all, that the time to act is now and we must work together to address this monumental challenge. This is the moral challenge of our generation."

UNEP Executive Director Achim Steiner said, "Many governments have asked to be kept abreast of the latest findings. I am sure that this report fulfils that request and will inform ministers' decisions when they meet in the Danish capital in only a few weeks time."

The Compendium reviews 400 major scientific contributions to the understanding of Earth systems and climate change that have been released through peer-reviewed literature, or from research institutions, over the past three years.

It shows that researchers have become increasingly concerned about ocean acidification due to the absorption of the greenhouse gas carbon dioxide in seawater and its impact on shellfish and coral reefs. Water that can corrode a shell-making substance called aragonite is already welling up along the California coast, decades earlier than predicted.

The observed increase in greenhouse gas concentrations is raising concern among some scientists that warming of between 1.4 and 4.3 degrees Celsius above pre-industrial surface temperatures could occur.

This exceeds the range of between one and three degrees perceived as the threshold for many "tipping points," including the end of summer Arctic sea ice, and the eventual melting of Himalayan glaciers and the Greenland ice sheet.

There is growing concern among some scientists that thresholds or tipping points may now be reached in a matter of years or a few decades, including dramatic changes to the Indian sub-continent's monsoon rains, the Sahara and West Africa monsoons, and climate systems affecting the Amazon rainforest.

The report indicates losses of tropical and temperate mountain glaciers affecting from 20 to 25 percent of the world's population in terms of drinking water, irrigation and hydro-power.

Shifts in the hydrological cycle are projected to result in the disappearance of regional climates with related losses of ecosystems, species and the spread of drylands northwards and southwards away from the equator.

Until the summer of 2007, most models projected an ice-free September for the Arctic Ocean towards the end of the current century. Reconsideration based on current trends has led to speculation that this could occur as soon as 2030.

Losses from glaciers, ice-sheets and the Polar Regions appear to be happening faster than anticipated, and melting of the Greenland Ice Sheet surface also seems to be accelerating. In the summer of 2007, the rate of melting was some 60 percent higher than the previous record in 1998.

Some scientists are now warning that sea levels could rise by up to two meters (6.5 feet) by 2100, drowning low-lying countries and coastal cities.

The loss of ice from West Antarctica is estimated to have increased by 60 percent in the decade to 2006, and by 140 percent from the Antarctic Peninsula in the same period.

Recent findings show that warming extends south of the Antarctic Peninsula, to cover most of West Antarctica, an area of warming much larger than previously reported.

The hole in the ozone layer has had a cooling effect on Antarctica, and is partly responsible for masking expected warming on the continent. The report warns that recovery of stratospheric ozone, due to the phasing out of ozone-depleting substances, is projected to increase Antarctic temperatures in coming decades.

Perennial drought conditions already have been observed in southeastern Australia and southwestern North America. Projections in the Compendium suggest that persistent water scarcity will increase in southern and northern Africa, the Mediterranean, much of the Middle East, a broad band across Central Asia and the Indian subcontinent.

A recent study projecting the impacts of climate change on the pattern of marine biodiversity suggests that ecosystems in sub-polar waters, the tropics and semi-enclosed seas will suffer numerous extinctions by 2050, while the Arctic and Southern Oceans will experience severe species invasions.

Marine ecosystems as a whole may see a species turnover of up to 60 percent, the Compendium indicates.

Up to 39 percent of the Earth's land surface could experience previously unknown climate conditions by 2100 and existing climates could disappear over as much as 48 percent of the planet's land surface.

Many of these "disappearing climates" coincide with biodiversity hotspots, and with the added problem of fragmented habitats and physical obstructions to migration, scientists project that many species will struggle to adapt to the new conditions.

Managing the effects of intensified global warming will require new measures, the Compendium indicates.

Management alternatives suggested include large-scale translocation or assisted colonization of species; eco-agriculture, in which landscapes are managed to sustain a range of ecosystem services, including food production; and the use of biochar, biologically-derived charcoal that is mixed in soils, increasing fertility and potentially locking up carbon for centuries.

Experts increasingly agree that active protection of tropical forests is a cost-effective means of cutting global emissions. An international mechanism of reducing emissions from deforestation and forest degradation, REDD, is likely to emerge as a central component of a new agreement in Copenhagen.

Still, many issues need to be resolved, such as how to verify the reductions and ensure fair treatment of local and indigenous forest communities.